As a beta tester I found the ground AI to be superior. If you look at my AARs in the Slitherine forum you can see that the AI took me to school a couple of times. As with any game I have personally played, the AI tends to be better on defense than on offense, although it is no slouch in the latter.

The air AI is better also, although I have occasionally found it to be slow in responding to blitzkrieg advances.

The naval AI is something that I personally did not spend a lot of time with, other than convoy raiding and ASW, in which cases the AI seemed up to the task.

We have put a lot of effort to improve the AI, to make it smarter, more aggressive and to use advantage from players mistakes. It is very tricky to learn AI how to choose what is more important and how to plan in longer period. Another thing is that this is a history wargame, and we have tried to make it realistic (do not mislead with simulation), without skinning it from fun. Also remember there is always difficulty setting for every country which allows to adjust the game for skills.

You can take a look at this AAR: http://www.slitherine.com/forum/viewtopic.php?t=29735&start=0 which has been played on a version close to the released one. If you will take a close look at some of the screens, you might see that the AI put a lot of effort to cut my units from the supply sources, and very often if it was possible, the AI advanced trough railroads.

As long as you are not overwhelming the enemy, it's become a real treat, and even if the AI is doomed, it is trying to use local advantages. You should not expect that the Polish AI will win with the German human player.

All in all I think we have done a good job until now and the future updates will make this game and AI even better.